Articles conveyed on inclined gravity-type roller conveyors over a substantial distance and slope accelerate as they advance along the conveyor and may attain a substantial velocity at the end of their traverse. The high velocity of the articles being conveyed is objectionable in that it presents various problems, such as the difficulty of stopping the articles, the damaging of the articles by impact with one another, and the tipping of the articles especially if they are relatively tall.
In an attempt to overcome the above problem, numerous gravity-type conveyors utilizing intermittently actuated brakes have been devised. However, conveyors of this type have had only limited commercial success.
One known gravity-type roller conveyor employing an intermittently actuated brake utilizes a plurality of rubber support rollers having internal brakes associated therewith for intermittently stopping the rollers. However, successful control of the rollers can be achieved only when the operating conditions are precisely controlled. When substantial temperature variations occur, the brakes do not always stop the rollers and thus proper control of the rollers, namely intermittent braking thereof, does not always result.
Another known roller conveyor uses an elongated brake member positioned below the rollers and moved upwardly by inflation of a flexible hose for engaging the rollers to periodically brake same. While this system is at least partially effective for controlling the rate of movement of the articles, nevertheless this system possesses undesirably structural and operational features. For example, the brake is applied only when the hose is inflated. Accordingly, when a failure in the inflating system or hose occurs, the brakes cannot be applied so that movement of the articles along the conveyor is uncontrolled. A further disadvantage is that the braking force applied to the rollers is determined solely by the pressure developed within the hose and by the relative clearances and distortions which occur throughout the system. The system clearances, distortions and hose pressure thus must be precisely controlled to result in the desired magnitude of braking.
To overcome the above disadvantages, Applicant devised an improved gravity-type roller conveyor utilizing an intermittently actuated roller system disposed for coaction with a stationary brake to provide for highly desirable speed control over heavy loads, specifically palletized loads, while additionally providing a fail-safe system. In this improved conveyor, the roller system is cyclically raised and lowered so that the loads are cyclically raised off of the stationary brake to permit a gravity-urged advance thereof along the conveyor, followed by lowering of the load onto the stationary brake, thereby achieving a high level of speed control over the loads.
While applicant's improved conveyor as above described has been observed to provide substantially improved speed control for heavy loads, such as palletized loads which may be in the order of several thousand pounds, nevertheless the mode of operation of this conveyor presents a further problem due to the fact that the rollers and the loads thereon are lifted upwardly during that portion of the cycle when the loads are permitted to advance along the conveyor. Because the loads are in this raised position during the advancing thereof, and inasmuch as loads often have a tendency to run crooked (that is, move sidewardly as they are being advanced along the conveyor), this improper tracking of the loads presents a serious problem in view of the continual raising and lowering of the loads during the normal conveyor operation. While conventional roller conveyors have traditionally been provided with upright side flanges adjacent the rollers for slidably guiding the conveyed articles and preventing sideward displacement thereof, nevertheless these upright guide flanges have long been recognized as undesirable since they create continual rubbing along one side of the article and hence not only create undesirable wear on both the flange and the article, but also introduce substantial undesired friction which undesirably impedes optimum operation of the conveyor. Further, use of such uprights flanges on applicant's conveyor, wherein the rollers and the loads are repetitively raised and lowered, would increase even further the undesirable wear and friction between the loads and the guide flanges, and would also greatly reduce the lifting capability of the roller system. Use of such guide flanges on a gravity conveyor employing a pulsating roller system which repetitively lifts and lowers is thus an unsatisfactory solution to the load misalignment problem.
Accordingly, it is an object of the present invention to provide an improved inclined roller conveyor of the type which permits for controlled intermittent movement of articles therealong by utilizing a stationary brake system positioned for direct engagement with the loads, with the movement of the loads being induced by a roller system which is periodically raised and lowered in a cyclical manner to cause corresponding lifting of the loads and re-engagement thereof with the stationary brake, and wherein the conveyor includes an improved alignment structure associated therewith which does not interfere with the free forward advance of the articles along the conveyor but which causes automatic recentering of the loads when they are being lowered toward the braking flanges to thereby correct for any misalignment which occurs during the step-like forward advances of the loads.
More specifically, the present invention provides an alignment system, as aforesaid, which preferably employs a pair of centering flanges which are fixed to and project outwardly and upwardly from the brake flanges so that the loads will be free of contact with the centering flanges during the normal forward advance along the conveyor, but in the event of any sideward misalignment of the load, then the lowering of the load toward the brake flanges will cause one side of the load to engage the respective centering flange, whereby the load will be automatically shifted sidewardly to effectively recenter same as it is deposited in engagement with the brake flanges. This thus prevents the load from dragging along the centering flanges during the normal forward advance of the load along the conveyor, thereby greatly minimizing wear and friction, while at the same time causing automatic engagement and recentering of only those loads which become misaligned or sidewardly displaced.
It is also an object of the present invention to provide an improved inclined roller conveyor of the gravity type having fail-safe brake means associated therewith for intermittently stopping the movement of the articles along the conveyor to control the movement rate, wherein the brake means includes an elongated brake rail disposed adjacent the rollers, wherein the rollers are movable between upper and lower positions disposed above and below the brake rail for enabling the conveyed articles to engage the brake rail when the rollers are in their lowered position, and wherein a control system causes the rollers to be periodically raised and lowered for causing the articles to be moved along the conveyor in an intermittent steplike manner to control the speed and movement thereof.
Other objects and purposes of the present invention will be apparent to persons acquainted with conveyors of this general type upon reading the following specification and inspecting the accompanying drawings.